Type II thyroxine 5'-deiodinase activity in the rat brown adipose tissue, pineal gland, Harderian gland, and cerebral cortex: effect of acute cold exposure and lack of relationship to pineal melatonin synthesis.
The effect of acute cold exposure for 6 hours on nocturnal type II thyroxine 5'-deiodinase (5'-D) activity was studied in brown adipose tissue (BAT), Harderian gland, cerebral cortex, and pineal gland of the rat. Moreover, the effect of iopanoic acid (IOP), a potent inhibitor of 5'-D activity, on both pineal N-acetyltransferase (NAT) activity and melatonin content in rats maintained in a cold environment was also examined. Results show that acute cold exposure significantly increases 5'-D activity in BAT but not in either the pineal gland, Harderian gland, or cerebral cortex. In all tissues, the injection of IOP reduced dramatically 5'-D activity, while exposure of the animals to light at night reduced 5'-D activity in pineal gland but not in either the Harderian gland or BAT while light exposure at night increased cerebrocortical 5'-D activity. Cold exposure did not change either pineal NAT activity or the melatonin content of the gland. Finally, when pineal 5'-D activity was inhibited by IOP treatment, neither nocturnal pineal NAT activity nor melatonin content was affected.
Guerrero
J M
JM
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
Santana
C
C
Reiter
R J
RJ
D000273:Adipose Tissue / Q000201:enzymology*; D000704:Analysis of Variance; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D002540:Cerebral Cortex / Q000201:enzymology*; D003080:Cold Temperature; D003624:Darkness; D006243:Harderian Gland / Q000201:enzymology*; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007480:Iopanoic Acid / Q000494:pharmacology; D008027:Light; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D010870:Pineal Gland / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains
D007453:Iodide Peroxidase; D001191:Arylamine N-Acetyltransferase; D007480:Iopanoic Acid; D008550:Melatonin